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In the current study, magnetic oxide nanoparticle-impregnated tea waste (TW-Fe3O4) is employed as an adsorbent to remove phosphate ions (PO43−) from an aqueous solution. By utilizing a variety of analytical methods, the TW-Fe3O4 nano-adsorbent was characterized by FE-SEM, TEM, EDX, BET, FTIR and XRD. The FE-SEM of TW-Fe3O4 demonstrated the adsorbent's granular morphology with a variety of magnetic nanoparticle sizes and shapes. The XRD of TW-Fe3O4 showed two diffraction peaks at 2θ values 30.9° and 35.4°, which are in correspondence with the diffraction pattern of magnetite. The synthesis of a TW-Fe3O4 adsorbent with a greater surface area and porosity was demonstrated by BET analysis. Numerous adsorption factors like initial concentration of PO43− ion, pH of the medium, contact time, temperature and adsorbent dose were optimized for phosphate removal. The maximum removal of 92% was achieved by using the adsorbent dose of 1.2 g at 323 K (pH 5). Pseudo-second-order and intra-particle diffusion models were fitted to the sorption kinetic, whereas adsorption isotherm data were found well fitted to Freundlich and Dubinin–Radushkevich (D-R) models. The highest adsorption capacity of TW-Fe3O4 towards phosphate ions was 226.8 mg/g, which is significantly higher than other reported bio-adsorbents. According to thermodynamic data, phosphate adsorption at the solid–liquid interface was of an endothermic and spontaneous nature and characterized by enhanced inevitability. [ABSTRACT FROM AUTHOR]

A highly efficient, quick and environmentally benign protocol has been adopted to synthesize AuNPs using the plant extract of Sueda fruciotosa . UV–vis spectroscopy, XRD, HRTEM, SEM and FTIR were used to characterize the prepared AuNPs. Different concentrations of plant extract were used to optimize the size, morphology and distribution of AuNPs. AuNPs were of small size and spheroid in shape at lower concentration. AuNPs showed a surface plasmon resonance at 443 nm. According to HRTEM the average size of AuNPs was 6–8 nm. The AuNPs were appraised for their photo degradation activity on methylene blue (MB) as an experimental substrate. Photo-catalytic activity of AuNPs was found to be dependent on the concentration of catalyst, irradiation time, size and aggregation of AuNPs. Furthermore, AuNPs exhibited an excellent electro-catalytic activity. The sensitivity of modified AuNPs was also studied for phenolic Azo dyes (PAD) which showed its good degradation activity. These gold nanoparticles found to be significantly applicable in the field of electrochemistry, sensors, catalysis, nano-devices, treatment of waste water and conversion of toxic agents into less toxic compound. [ABSTRACT FROM AUTHOR]

Removal of chlorendic acid, an emerging water pollutant and potential carcinogenic, was investigated by gamma radiation in the absence and presence of peroxymonosulfate (PMS, HSO 5 − ). The removal of chlorendic acid (1.40 μM initial concentration) by gamma radiation was promoted with PMS, i.e., 95% compared to 82% in the absence of PMS, at an absorbed dose of 1000 Gy. The removal of chlorendic acid by gamma-ray/PMS process was due to OH and SO 4 − . Second-order rate constants of 5.90 × 10 9 , 1.75 × 10 9 , and 2.05 × 10 9 M −1 s −1 for chlorendic acid with e aq − , OH, and SO 4 − , respectively, were determined. The removal efficiency of chlorendic acid was promoted with increasing initial PMS concentration and decreasing initial target contaminant concentration. The removal of chlorendic acid by gamma-ray/PMS was inhibited in the presence of CO 3 2− , NO 2 − , p -CBA, m -TA, and alcohols. The presence of Fe 2+ , Cu + , and Fe 3+ with gamma-ray/PMS promoted removal efficiency of chlorendic acid from 78% to 99, 94, and 89%, respectively, at 592 Gy. The degradation of chlorendic acid by OH and SO 4 − was found to be initiated at the carboxylate group as could be revealed from nature of the transformation by-products. Nevertheless, this study concluded that gamma-ray/PMS is of practical importance in treatment of natural water containing chlorendic acid, as potential detoxification of chlorendic acid solution can be revealed from 83% loss of chloride ion at 3000 Gy. In addition, gamma-ray/PMS process achieved efficient removal of chlorendic acid even in the presence of commonly found inorganic ions in natural water. [ABSTRACT FROM AUTHOR]

This study investigated iron-mediated oxidative processes for the photochemical degradation of endosulfan, a chlorinated insecticide and central nervous system disruptor. At UV fluence of 360 mJ/cm 2 , 52.4% and 32.0% removal of 2.45 μM initial endosulfan was observed by UV/Fe 3+ and UV/Fe 2+ processes, respectively, at an initial concentration of 17.8 μM iron. The degradation of endosulfan by UV/Fe 3+ or UV/Fe 2+ was dramatically enhanced by adding peroxide (i.e., H 2 O 2 , S 2 O 8 2− or HSO 5 − ). Among the UV/peroxide/Fe processes, the highest degradation efficiency of 99.0% at UV fluence of 360 mJ/cm 2 was observed by UV/HSO 5 − /Fe 2+ with 2.45 μM [endosulfan] 0 , 17.8 μM [Fe 2+ ] 0 , and 49.0 μM [HSO 5 − ] 0 . The observed degradation rate constant of endosulfan was promoted either by increasing [Fe 2+ ] 0 and/or [peroxide] 0 or by decreasing [endosulfan] 0 , while the initial degradation rate of endosulfan increased with increasing [Fe 2+ ] 0 , [peroxide] 0 , or [endosulfan] 0 . At UV fluence of 6000 mJ/cm 2 , 45.0% mineralization as represented by the decrease in total organic carbon content was observed by UV/HSO 5 − /Fe 2+ at 9.80 μM [endosulfan] 0 , 980 μM [HSO 5 − ] 0 , and 17.8 μM [Fe 2+ ] 0 . The major by-product of endosulfan was observed in all cases to be endosulfan ether which was further degraded with an extended reaction time. The results suggest that iron-mediated advanced oxidation processes (AOPs) have a high potential for the removal of endosulfan and its by-product from contaminated water. [ABSTRACT FROM AUTHOR]

Desethyl-atrazine (DEA) and desisopropyl-atrazine (DIA) are the two major degradation by-products of atrazine (a suspected human carcinogen and endocrine disrupting herbicide), and show an equal toxicity to their parent compound. This study investigated the degradation of DEA and DIA with OH and SO 4 − generated from the activation of peroxides, i.e., persulfate (S 2 O 8 2− ), peroxymonosulfate (HSO 5 − ) and hydrogen peroxide (H 2 O 2 ), by UV-254 nm radiation in the presence or absence of Fe 2+ . Quantum yields of DEA and DIA were independent of pH (3.0–11.0). The higher quantum yield of reactive radicals from UV/S 2 O 8 2− , i.e., 1.8 compared to 1.04 for UV/HSO 5 − and 1.0 for UV/H 2 O 2 , resulted in greater efficiency of UV/S 2 O 8 2− for both DEA and DIA degradation. The second-order rate constants of DEA and DIA with SO 4 − were calculated to be (6.42 ± 0.12) × 10 8 and (1.70 ± 0.30) × 10 9 M −1 s −1 , and that with OH were (1.14 ± 0.09) × 10 9 and (2.22 ± 0.44) × 10 9 M −1 s −1 , respectively, suggesting a strong impact of side chains toward radical reactions. Fe 2+ promoted slightly the activation of the examined peroxides at pH 7.4. Presence of organic matter and alkalinity in field water samples negatively influenced the efficiency of UV/S 2 O 8 2− . Based on the identified degradation by-products by GC–MS, potential degradation pathways were proposed for both compounds. The results obtained suggested that DEA and DIA can be efficiently removed from the contaminated water by OH and SO 4 − based-AOPs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Degradation of atrazine was investigated in UV, UV/H2O2, UV/HSO5 − and UV/S2O8 2− AOPs. [•] UV/S2O8 2− process was found to be more efficient as well as more economical. [•] The pH affected UV/S2O8 2− but had no significant influence on UV, UV/H2O2 and UV/HSO5 −. [•] Second order rate constants of atrazine with SO4 − and OH were found to be comparable. [•] Degradation mechanism was investigated by GC–MS and LC–MS/MS analysis. [ABSTRACT FROM AUTHOR]

Abstract: The degradation of atrazine, a widely used endocrine disrupting, carcinogenic and persistent herbicide, was investigated by photo-Fenton and photo-Fenton-like advanced oxidation technologies (AOTs): UV/H2O2/Fe2+, UV//Fe2+ and UV//Fe2+. The study was carried out at two pH value conditions, i.e., pH 3.0 and pH 5.8. At pH 3.0, UV//Fe2+ was found to be the most efficient technology whereas UV//Fe2+ was observed to be the most effective at pH 5.8. The degradation of atrazine followed pseudo-first-order reaction with the highest observed rate constant of 2.00×10−2 cm2/mJ in UV//Fe2+ system at the initial concentrations of 4.64μM atrazine, 46.4μM (PMS) and 35.81μM Fe2+. The UV fluence required for the complete removal of 4.64μM atrazine at initially 92.80μM of oxidant and 8.95μM of Fe2+ concentrations at pH 3.0 was found to be 480, 720 and 960mJ/cm2 in UV//Fe2+, UV//Fe2+ and UV/H2O2/Fe2+ systems, respectively. Humic and fulvic acids were found to negatively impact the degradation of atrazine. The removal of TOC was not significant unless a high UV fluence was applied. At an initial concentration of 18.56μM atrazine, 1856.00μM oxidant and 17.91μM Fe2+, a 62.94%, 47.10% and 44.09% decrease in TOC was achieved at a UV fluence of 6000mJ/cm2 in UV/PS/Fe2+, UV/PMS/Fe2+ and UV/H2O2/Fe2+ systems, respectively. Nevertheless, it is suggested in this study that photo-Fenton and photo-Fenton-like technologies are capable of removing atrazine from water efficiently. [Copyright &y& Elsevier]

Organochlorine pesticides (OCPs) have been used extensively as insecticides and herbicides. This study investigates the occurrence of lindane in surface water from the Peshawar valley ( i.e. , Peshawar, Charsadda, Nowshera, Mardan and Swabi districts of Khyber Pakhtunkhwa, Pakistan). Out of 75 samples tested ( i.e. , 15 samples from each district), 13 samples (including 2 from Peshawar, 3 from Charsadda, 4 from Nowshera, 1 from Mardan, and 3 from Swabi) are found to be contaminated with lindane. Overall, the detection frequency is 17.3%. The maximum concentration of lindane is detected in a water sample from Nowshera and found to be 2.60 μg L -1 . Furthermore, the degradation of lindane in the water sample from Nowshera, containing the maximum concentration, is investigated by simulated solar-light/TiO 2 (solar/TiO 2 ), solar/H 2 O 2 /TiO 2 and solar/persulfate/TiO 2 photocatalysis. The degradation of lindane by solar/TiO 2 photocatalysis is 25.77% after 10 h of irradiation. The efficiency of the solar/TiO 2 process is significantly increased in the presence of 500 μM H 2 O 2 and 500 μM persulfate (PS) (separately), represented by 93.85 and 100.00% lindane removal, respectively. The degradation efficiency of lindane is lower in natural water samples as compared to Milli-Q water, attributed to water matrix effect. Moreover, the identification of degradation products (DPs) shows that lindane follows similar degradation pathways in natural water samples as the one in Milli-Q water. The results show that the occurrence of lindane in surface waters of Peshawar valley is a matter of great concern for human beings and the environment. Interestingly, H 2 O 2 and PS assisted solar/TiO 2 photocatalysis is an effective method for the removal of lindane from natural water., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

This study reported Fe doped zinc oxide (Fe-ZnO) synthesis to degrade chlorpyrifos (CPY), a highly toxic organophosphate pesticide and important sources of agricultural wastes. Fourier transform infrared, X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectroscopic analyses showed successful formation of the Fe-ZnO with highly crystalline and amorphous nature. Water collected from agricultural wastes were treated with Fe-ZnO and the results showed 67% degradation of CPY by Fe-ZnO versus 39% by ZnO at 140 min treatment time. Detail mechanism involving reactive oxygen species production from solar light activated Fe-ZnO and their role in degradation of CPY was assessed. Use of H 2 O 2 , peroxydisulfate (S 2 O 8 2- ) and peroxymonosulfate (HSO 5 - ) with Fe-ZnO under solar irradiation promoted removal of CPY. The peroxides yielded hydroxyl (OH) and sulfate radical () under solar irradiation mediated by Fe-ZnO. Effects of several parameters including concentration of pollutant and oxidants, pH, co-existing ions, and presence of natural organic matter on CPY degradation were studied. Among peroxides, HSO 5 - revealed to provide better performance. The prepared Fe-ZnO showed high reusability and greater mineralization of CPY. The GC-MS analysis showed degradation of CPY resulted into several transformation products (TPs). Toxicity analysis of CPY as well as its TPs was performed and the formation of non-toxic acetate imply greater capability of the treatment technology., (Copyright © 2021 Elsevier Ltd. All rights reserved.)